Semiconductor device having carbon nanotubes and method for manufacturing the same

Abstract

A semiconductor device having good switching characteristics even metallic CNTs are included and a manufacturing method thereof are provided. The semiconductor device includes a source electrode; a drain electrode; and a channel layer formed between the source electrode and the drain electrode and including a carbon nanotube group. The carbon nanotube group includes conductive carbon nanotubes having a characteristic of a conductive material and semiconductive carbon nanotubes having a characteristic of a semiconductive material. The density of the carbon nanotube group is the density where the source electrode and the drain electrode are connected to each other through all of the carbon nanotube group and not connected to each other only through the conductive carbon nanotubes.

1. A manufacturing method of a semiconductor device comprising:
 designing a distance between a source electrode and a drain electrode; 
 preparing a carbon nanotube group including both of conductive carbon nanotubes having a characteristic of a conductive material and semiconductive carbon nanotubes having a characteristic of a semiconductive material; and 
 forming a channel layer by depositing the carbon nanotube group on a channel layer forming region at a density where the source electrode and the drain electrode are connected to each other through all of the carbon nanotube group and not connected to each other only through the conductive carbon nanotubes, 
 wherein the preparing comprises preparing the carbon nanotube group in which the conductive carbon nanotubes accounts for 1/k of total of carbon nanotubes, and the forming the channel layer comprises:
 preparing a first data indicating a correspondence relationship between a short-circuit probability being a probability of a short-circuit of the source electrode and the drain electrode through carbon nanotubes and a density of carbon nanotubes for each length of carbon nanotubes; 
 determining ρ open and ρ short by referring the first data for each length of carbon nanotubes, wherein the ρ open indicates a maximum value of a density of carbon nanotubes at which the source electrode and the drain electrode are substantially opened to each other, and the ρ short indicates a minimum value of a density of carbon nanotubes at which the source electrode and the drain electrode are substantially short-circuited to each other; 
 determining a length of carbon nanotubes at which the ρ short is smaller than k×ρ open; 
 adjusting a length of the prepared carbon nanotube group to a length determined at the step of determining the length; and 
 forming the channel layer by depositing the carbon nanotube group adjusted at the adjusting on the cannel layer forming region such that a density of carbon nanotubes ρ total is in a range represented by ρ short<ρ total<k×ρ open. 
 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein the carbon nanotube group includes ⅔ or more of the semiconductive carbon nanotubes against whole carbon nanotubes. 
     
     
       3. The semiconductor device according to  claim 1 , wherein the conductive carbon nanotubes in the carbon nanotube group included in the channel layer is oriented in a direction perpendicular to a direction connecting the source electrode and the drain electrode. 
     
     
       4. The manufacturing method of the semiconductor device according to  claim 1 , wherein at the step of preparing the carbon nanotube group, the carbon nanotube group whose k is 3 is prepared. 
     
     
       5. The manufacturing method of the semiconductor device according to  claim 1 , wherein the length of carbon nanotubes determined at the determining the length of carbon nanotubes is 30% or less compared with a distance between the source electrode and the drain electrode. 
     
     
       6. A manufacturing method of a semiconductor device comprising:
 designing a distance between a source electrode and a drain electrode; 
 preparing a carbon nanotube group including both of conductive carbon nanotubes having a characteristic of a conductive material and semiconductive carbon nanotubes having a characteristic of a semiconductive material; and 
 forming a channel layer by depositing the carbon nanotube group on a channel layer forming region at a density where the source electrode and the drain electrode are connected to each other through all of the carbon nanotube group and not connected to each other only through the conductive carbon nanotubes, 
 wherein the preparing the carbon nanotube group comprises preparing the carbon nanotube group in which the conductive carbon nanotubes accounts for 1/k of total of carbon nanotubes, and the forming the channel layer comprises:
 preparing a first data indicating a correspondence relationship between a short-circuit probability being a probability of a short-circuit of the source electrode and the drain electrode through carbon nanotubes and a density of carbon nanotubes for each length of carbon nanotubes; 
 generating a second data by normalizing the first data for a density of carbon nanotubes corresponding to the short-circuit probability being 0.5 to be 1 for each length of carbon nanotubes; 
 calculating a standard deviation σ by matching the second data with an error function for each length of carbon nanotubes; 
 calculating ρ open as “1−ασ” and ρ short as “1+ ασ ” (α is a predetermined coefficient) respectively; 
 determining a length of carbon nanotubes for satisfying ρ<(k−1)/{α(1+k)}; 
 adjusting a length of the prepared carbon nanotube group to a length determined at the determining the length; and 
 forming the channel layer by depositing the carbon nanotube group adjusted at the adjusting on the cannel layer forming region such that a density of carbon nanotubes ρ total is in a range represented by ρ short<ρ total<k×ρ open. 
 
 
     
     
       7. A manufacturing method of a semiconductor device comprising:
 designing a distance between a source electrode and a drain electrode; 
 preparing a carbon nanotube group including both of conductive carbon nanotubes having a characteristic of a conductive material and semiconductive carbon nanotubes having a characteristic of a semiconductive material; and 
 forming a channel layer by depositing the carbon nanotube group on a channel layer forming region at a density where the source electrode and the drain electrode are connected to each other through all of the carbon nanotube group and not connected to each other only through the conductive carbon nanotubes, 
 wherein the preparing the carbon nanotube group comprises preparing the carbon nanotube group in which the conductive carbon nanotubes accounts for 1/k of total of carbon nanotubes, and the forming the channel layer comprises:
 determining a density ρ× of carbon nanotubes at which g(ρ) represented by a following equation is a minimum:
     g (ρ)=1− f (ρ)+ f (ρ× k )
 
 
 in which f(ρ) is a function of a carbon nanotube density ρ representing a short-circuit probability indicating a probability of an establishment of a connection between the source electrode and the drain electrode through carbon nanotubes; and 
 forming the channel layer by depositing the carbon nanotube group prepared at the preparing the carbon nanotube group on the channel layer forming region to a density of carbon nanotubes be the ρ×. 
 
 
     
     
       8. The semiconductor device according to  claim 7 , wherein the carbon nanotube group includes ⅔ or more of the semiconductive carbon nanotubes against whole carbon nanotubes. 
     
     
       9. The semiconductor device according to  claim 7 , wherein the conductive carbon nanotubes in the carbon nanotube group included in the channel layer is oriented in a direction perpendicular to a direction connecting the source electrode and the drain electrode. 
     
     
       10. The manufacturing method of the semiconductor device according to  claim 6 , wherein α is equal to or more than 3. 
     
     
       11. The semiconductor device according to  claim 6 , wherein the carbon nanotube group includes ⅔ or more of the semiconductive carbon nanotubes against whole carbon nanotubes. 
     
     
       12. The semiconductor device according to  claim 6 , wherein the conductive carbon nanotubes in the carbon nanotube group included in the channel layer is oriented in a direction perpendicular to a direction connecting the source electrode and the drain electrode.